Guide catheters for accessing cardiac sites

ABSTRACT

A method and apparatus for introducing a cardiac lead to an implantation site that includes a catheter body having an outer wall and a distal leader and having a proximal portion extending from the first proximal end to a second distal end. An inner member is positioned within an outer lumen of the catheter body and is spaced from the outer wall to form a first inner lumen for receiving a guide tool inserted therein and a second lumen for receiving the cardiac lead while the guide tool is positioned within the first inner lumen. A distal end of the inner member forms a first opening at a distal end of the first inner lumen and a second opening at a distal end of the second inner lumen, the first opening and the second opening positioned proximal the distal leader.

TECHNICAL FIELD

The present invention relates to bilumen guide catheters forintroduction and implantation of cardiac leads for applying electricalstimulation to and/or sensing electrical activity of the heart or theintroduction of other medical instruments and materials into cardiacvessels.

BACKGROUND

Implantable permanent and temporary medical electrical stimulationand/or sensing leads are well known in the fields of cardiac stimulationand monitoring, including cardiac pacing andcardioversion/defibrillation, and in other fields of electricalstimulation or monitoring of electrical signals or other physiologicparameters. In the field of cardiac stimulation and monitoring, theelectrodes of epicardial or endocardial cardiac leads are affixedagainst the epicardium or endocardium, respectively, or insertedtherethrough into the underlying myocardium of the heart wall.

It has become possible to reduce endocardial lead body diameters from 10to 12 French (3.3 to 4.0 mm) down to 2 French (0.66 mm) presentlythrough a variety of improvements in conductor and insulator materialsand manufacturing techniques. The lead bodies of such small diameter, 2French, endocardial leads are formed without a lumen that accommodatesuse of a stiffening stylet to assist in implantation.

These small diameter endocardial pacing and cardioversion/defibrillationleads are advantageously sized to be advanced into the coronary sinus tolocate the distal electrode(s) adjacent to the left atrium or intocoronary veins branching from the coronary sinus to locate the distalelectrode(s) adjacent to the left ventricle. The distal end of such acoronary sinus lead is advanced through the superior vena cava, theright atrium, the valve of the coronary sinus, the coronary sinus, and,if employed to pace or sense the left ventricle, into a cardiac veinbranching from the coronary sinus.

Typically, such small diameter endocardial leads are formed with anactive fixation helix that extends distally and axially in alignmentwith the lead body to a sharpened distal tip and that has a helixdiameter substantially equal to the lead body diameter. The fixationhelix does not necessarily increase the overall diameter of theendocardial lead and is relatively robust, once the helix is screwedinto the myocardium. Typically, but not necessarily, the fixation helixis electrically connected to a lead conductor and functions as apace/sense electrode. In some cases, the lead body encloses one or morehelical coiled or stranded wire conductor and lacks a lumen.

The lead bodies of such small diameter endocardial screw-in leads can beso supple and flexible that it is difficult to rotate the lead distalend by application of rotary torque to the lead proximal end unless thelead body remains relatively straight and not confined by contact withvessel walls. This diminished “torqueability” prevents the rotation ofthe fixation helix at the lead distal end or renders the rotationdifficult once the lead body is advanced through a tortuous pathway andconfined by contact against the vessel walls. In addition, such leadbodies may also possess little if any column strength and lack“pushability”, that is the ability to advance the lead distal endaxially when the lead proximal end is pushed axially, particularly whenthe lead body extends through the tortuous transvenous pathway. Thus, ithas been found necessary to use implantation instruments or tools thatcompensate for the lack of pushability and torqueability of the leadbody.

Once the implantation site is reached in coronary vasculature, it isdifficult to aim the distal fixation mechanism toward myocardial tissue,and the fixation mechanism may inadvertently be aimed at and deployedaway from the myocardium. The pace/sense electrodes may not besufficiently in contact with excitable cardiac tissue, resulting inunduly high stimulation thresholds and diminished sensing.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects and features of the present invention will be readilyappreciated as the present invention becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings, in which like referencenumerals designate like parts throughout the figures thereof andwherein:

FIG. 1 is a schematic diagram of a heart from an anterior perspectiveillustrating the coronary venous system about an epicardial surface ofthe heart, including dashed lines depicting a portion of coronary venoussystem on an opposite, posterior epicardial surface of the heart;

FIG. 2 is a plan view, in partial exposed section, of a typical pacinglead that can be introduced and affixed in the coronary venous systememploying a bilumen guide catheter and method of the present invention;

FIG. 3 is a plan view of a guidewire and an over-the-wire bilumen guidecatheter in accordance with a first embodiment of the invention adaptedto be advanced through the tortuous pathway from outside the patient'sbody to the implantation sites illustrated in FIG. 1, for example, overthe guidewire;

FIG. 4 is a partial view of a distal segment of the catheter body ofFIG. 3 depicting the leader, the delivery lumen exit port, and theguidewire extending from the guide lumen exit port;

FIG. 5 is a cross-section view taken along lines 5-5 in FIG. 4 depictingthe shape of at least a portion of the catheter body to preferentiallyurge the delivery catheter lumen exit port toward the vessel wall andthe underlying heart and away from the pericardium and pericardial spaceduring advancement of the guide catheter body through coronary vesselsdepicted in FIG. 1;

FIG. 6 is a cross-section view taken along lines 6-6 in FIG. 4 depictingthe shape of the delivery catheter lumen exit port to urge the distalfixation helix of the cardiac lead of FIG. 2 toward the vessel wall andthe underlying heart and away from the pericardium and pericardial spaceduring advancement of the guide catheter body through coronary vesselsdepicted in FIG. 1;

FIG. 7 is a partial perspective view of a further embodiment of abi-lumen catheter body adapted to be combined with a hub of the typedepicted in FIG. 3, the catheter body shaped to optimally dispose thedelivery lumen exit port toward the heart;

FIG. 8 is a partial schematic illustration of the disposition of thedelivery lumen exit port of the catheter body of FIG. 7 toward the heartto affix the fixation helix of the cardiac lead of FIG. 2 when the guidecatheter body is advanced through the tortuous pathway from outside thepatient's body to the implantation sites illustrated in FIG. 1;

FIG. 9 is a partial plan view of a multi-lumen catheter body having atleast two delivery lumens that is adapted to be substituted for thecatheter body of the guide catheter of FIG. 3, with suitablemodification of the hub;

FIG. 10 is a partial schematic illustration of the disposition of thedelivery lumen exit ports of the catheter body of FIG. 9 toward theheart to affix the fixation helices of two cardiac leads of FIG. 2 whenthe guide catheter body is advanced through the tortuous pathway fromoutside the patient's body to the implantation sites illustrated in FIG.1;

FIG. 11 is a partial perspective view of a further embodiment of abi-lumen catheter body adapted to be combined with a hub of the typedepicted in FIG. 3, the catheter body shaped to optimally dispose thedelivery lumen exit port toward the heart;

FIG. 12 is a cross-section view taken along lines 12-12 of FIG. 11depicting one form of internal shaping of the catheter body proximalportion;

FIG. 13 is a partial schematic illustration of the disposition of thedelivery lumen exit port of the catheter body of FIG. 11 toward theheart to affix the fixation helix of the cardiac lead of FIG. 2 when theguide catheter body is advanced through the tortuous pathway fromoutside the patient's body to the implantation sites illustrated in FIG.1;

FIG. 14 is a cross-section view taken along lines 12-12 of FIG. 11depicting a further form of internal shaping of the catheter bodyproximal portion;

FIG. 15 is a cross-sectional view of a catheter body according to anembodiment of the present invention; and

FIG. 16 is a cross-sectional view of a catheter body according to anembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, references are made toillustrative embodiments for carrying out the invention. It isunderstood that the drawing figures are not necessarily to scale andthat other embodiments may be utilized without departing from the scopeof the invention. The invention and its preferred embodiments may beemployed in implantation of unipolar, bipolar or multi-polar,endocardial, cardiac pacing leads, cardioversion/defibrillation leads ormonitoring leads having one or more pace/sense electrode(s) or senseelectrode(s), respectively, at or adjacent the distal lead end and anactive fixation mechanism that is to be affixed into the myocardium.Moreover, other sensors for sensing a physiologic parameter may beincorporated into the lead body. An insulated electrical conductorextending proximally through the lead body to connector element of alead proximal end connector assembly is coupled to each such pace/senseelectrode, sense electrode, cardioversion/defibrillation electrode andsensor. The proximal connector assembly is adapted to be coupled to theconnector assembly of an external medical device, including an externalpacemaker or monitor, or an implantable medical device, including an IPGfor pacing, cardioversion/defibrillation (or both) or an implantablemonitor. Therefore, it will be understood that the arrangement forintroduction of a cardiac lead of the present invention can be employedto introduce permanently implantable and temporary cardiac leads of anyof these types, particularly within the coronary vasculature.

The multi-lumen guide catheters and methods of the present invention areparticularly useful in introducing such small diameter cardiac leadsthat are devoid of a stylet lumen and are so flexible and possess suchlow column strength, rigidity, pushability and torqueability that thelead distal end cannot be advanced transvenously and positioned at thedesired implantation site without assistance. Moreover, one particularuse of the arrangement of the present invention is to introduce suchcardiac leads that are formed using stranded wire conductor(s) within alead body diameter of about 0.010-0.026 inches of the type described inthe above-incorporated, commonly assigned, '014 patent. The lead bodyouter diameter is minimized by use of such conductors and by eliminatingthe lumen for receiving a stiffening stylet. However, the arrangement ofthe present invention can also be employed to introduce cardiac leadsthat employ coiled wire conductors with or without a lumen for receivinga stiffening stylet. In the latter case, the stiffening stylet need notbe used to achieve the introduction.

FIG. 1 is a schematic diagram of a heart 6 from an anterior perspectiveillustrating a coronary venous system about an epicardial surface,including dashed lines depicting a portion of coronary venous system onan opposite, posterior surface of the heart 6. FIG. 1 also illustrates apathway, defined by arrow ‘A’, which may be followed in order to place acardiac lead within CS 4, extending from a venous access site (notshown) through the superior vena cava (SVC) 1 into the right atrium (RA)2 of heart 6 and from the RA 2 into the CS 4 through a coronary sinusostium (CS Os) 3.

As illustrated in FIG. 1, the coronary venous system of a heart 6includes the CS 4 and vessels branching therefrom including the middlecardiac vein (MCV) 13, the posterior cardiac vein (PCV) 12, theposterior-lateral cardiac vein (PLV) 11, the great cardiac vein (GCV) 9,and the lateral cardiac vein (LCV) 10 all branching away from the CS 4.Generally speaking, the distal portion of the CS 4 and the branchingvessels including at least portions of the MCV 13, PCV 12, the PLV 11,the GCV 9, and the LCV 10 overlie the or are embedded within theepicardium that defines outer surface of the heart 6 and encases heartmuscle or myocardium. Portions of the epicardium are spaced from asurrounding pericardial sac or pericardium (not shown), whereby apericardial space surrounds the spaced epicardium of heart 6. Thus, thevessel walls of the distal portion of the CS 4 and the branching vesselsincluding at least portions of the MCV 13, PCV 12, the PLV 11, the GCV9, and the LCV 10 are partially exposed to the pericardial space oradhered to the pericardium and are partially embedded against theunderlying myocardium. For convenience of terminology, the vessel wallsthat are disposed toward the pericardium are referred to as disposed“away from the heart”, whereas the vessel walls that are disposed towardthe myocardium are referred to as disposed “toward the heart”.

In patients suffering from heart failure, a CS lead of the typesdescribed above is advanced through the pathway “A” extending throughthe SVC 1 and RA 2 into the CS 4 to dispose one or a pair of distalpace/sense electrodes at an LV site(s) within one of the vesselsbranching from the CS 4. An RV lead is advanced through the SVC 1, theRA 2, the tricuspid valve, and the distal pace/sense electrode(s) isaffixed at an RV pace/sense site(s) of the RV 8, e.g., in the RV apex oralong the septum separating the RV and LV chambers. The RV lead can takeany of the functions known in the art preferably having an active orpassive fixation mechanism.

The proximal connectors of the CS lead and the RV lead are coupled to aconnector header of a pacing IPG or an ICD IPG (not shown) implantedsubcutaneously. The IPG is capable of sensing and processing cardiacsignals detected at the pace/sense site(s) to provide synchronized RVand LV pacing at the pace/sense sites as needed. The pacing and sensingfunctions of such an IPG that provides synchronous activation of the RV8 and LV 7 in order to improve the hemodynamic output of the heart 6 aredisclosed in commonly assigned U.S. Pat. No. 5,902,324, for example, andare embodied in the MEDTRONIC® InSync Marquis™ ICD IPG, for example.

Hemodynamic output is enhanced when the CS pace/sense electrode(s) siteis selected within a late activated region of LV 7. Late activatedregions of the LV 7 are found within the myocardium underlying the PLV11, the LCV 10, the GCV 9, or the CS 4 near a junction with the GCV 9.Moreover, pacing and sensing functions are optimized when the pace/senseelectrode(s) are disposed in intimate contact with excitable myocardialtissue.

The lead body of a permanent or temporary cardiac lead typicallyincludes one or more insulated conductive wire surrounded by aninsulating outer sheath. Each conductive wire couples a proximal leadconnector element with a distal stimulation and/or sensing electrode.Temporary and permanent cardiac leads having a single stimulation and/orsensing electrode at the lead distal end, a single conductor, and asingle connector element are referred to as unipolar cardiac leads.Temporary and permanent cardiac leads having two or more stimulationand/or sensing electrodes at the lead distal end, two or more respectiveconductors, and two or more respective connector elements are referredto as bipolar lead or multi-polar leads, respectively.

A typical example of an active fixation cardiac lead 20 that can beintroduced through a bilumen guide catheter of the present inventionadvanced through pathway “A” and employed as a CS lead is schematicallyillustrated in FIG. 2. The cardiac lead 20 can also be introduced asdescribed above into the RV to function as an RV lead. The cardiac lead20 has an elongated lead body 21 that extends between a proximalconnector 22 and a distal end 24. A helical fixation element or helix 25having a sharpened piercing tip 251 extends distally from lead bodydistal end 24. Pacing lead 20 is essentially iso-diametric along itslength, with an outer diameter of lead body 21 and fixation helix 25between approximately 1 French (0.33 mm) to 3 French (1.00 mm). Sincelead body 21 does not include an inner lumen, the outer diameter of leadbody 21 is reduced.

Lead body 21 is constructed of a stranded conductive or non-conductivefilament cable 28 disposed within an inner sheath lumen of an innersheath 29, which in turn extends through the coil lumen of a coil 27.The assembly of the coil 27, inner sheath 29, and cable 28 is fittedthrough an outer sheath lumen of an outer sheath 26.

Coil 27 is formed of any bio-stable and biocompatible material that issufficiently stiff to provide adequate torque transfer from proximalconnector assembly 22 to fixation element 25 at distal end 24 of cardiaclead 20. When coil 27 functions as a lead conductor, coil 27 ispreferably formed of single or multiple wire filars made of MP35-Nalloy, well known in the art, or any other bio-stable and biocompatiblematerial that is capable of reliably conducting electrical current afterhaving been subjected to numerous, repeated bending and torsionalstresses.

Inner cable 28 is formed from synthetic filaments or conductive metallicwires, when inner cable functions as a lead conductor. The proximal anddistal ends of inner cable 28 are coupled to connector pin 23 or withinconnector assembly 22 and fixation helix 25, respectively, to providetensile strength to lead body 21.

Outer sheath 26 is formed of either a silicone rubber or polyurethane,well known in the art, or any other flexible, bio-stable andbiocompatible, electrically insulating, polymer material. Inner sheath29 is similarly formed of a bio-stable and biocompatible flexiblepolymer coating or tube that protects inner cable 28 from mechanicalstresses or degradation and electrically insulates inner cable 28 fromcontact with wire coil 27. Inner sheath 29 can be formed of flexible,bio-stable and biocompatible electrically insulating materials known inthe art, including silicone rubber compounds, polyurethanes, andfluoropolymers.

In both unipolar and bipolar cardiac lead embodiments, the proximalconnector assembly 22 includes a connector pin 23 that is typicallyelectrically connected with the distal fixation helix 25 when the distalfixation helix 25 functions as a pace/sense electrode. In a bipolarcardiac lead embodiment, the proximal connector assembly 22 includes aconnector ring 32 (shown with dashed lines) that is electrically coupledto a ring-shaped pace/sense electrode 30 (shown with dashed lines)supported by outer sheath 26 proximal to fixation helix 25. Theconnector assembly 22 is shaped to be inserted into a bore of aconnector block of the connector header of an IPG as described above tomake an electrical connection between the distal pace/sense electrode(s)and IPG sensing and/or pacing pulse generating circuitry. Ring-shapedpace/sense electrode 30 is preferably formed of a platinum alloy butother materials may also be used, including but not limited to suchmaterials as palladium, titanium, tantalum, rhodium, iridium, carbon,vitreous carbon and alloys, oxides and nitrides of such metals or otherconductive or even semi-conductive materials. Of course, some materialsare incompatible with others and may not be effectively used together.The limitations of specific materials for use with others are well knownin the art.

The fixation helix 25 is adapted to be screwed into the myocardium, asdescribed below, by rotation of lead body 21 from the proximal connectorassembly 22 when piercing tip 251 is advanced to and oriented toward afixation site. When fixation helix 25 functions as a pace/senseelectrode, as in alternate embodiments described above, fixation helix25 is preferably formed of a platinum iridium alloy, although it isunderstood that other biocompatible and bio-stable materials may also beused, including but not limited to such materials as palladium,titanium, tantalum, rhodium, carbon, vitreous carbon and alloys, oxidesand nitrides of such metals or other conductive or even semi-conductivematerials well known in the art.

In a unipolar embodiment of cardiac lead 20, the inner cable 28 isnonconductive, a proximal end of coil 27 is coupled to connector pin 23,and a distal end of coil 27 is coupled to the proximal end of fixationhelix 25. The proximal and distal ends of coil 27 are welded or crimpedto the connector pin 23 and fixation helix 25, respectively, usingcommon welding or crimping techniques known in the art. The proximal anddistal ends of inner cable 28 are crimped to the connector pin 23 orconnector assembly 22 and fixation helix 25, respectively, using commonwelding or crimping techniques known in the art.

In an alternate unipolar embodiment wherein the inner cable isnonconductive, helix fixation element 25 simply provides fixation anddoes not function as a pace/sense electrode. The proximal end of coil 27is coupled to connector pin 23, and the distal end of coil 27 is coupledto the ring-shaped pace/sense electrode 30 incorporated coaxially abouta distal portion of lead body 21. The spacing 31 between ring-shapedpace/sense electrode 30 and fixation helix 25 is less than approximately0.02 inches, in order to locate ring-shaped pace/sense electrode 30close enough to a fixation site for tissue contact when fixation helix25 is fixed into the myocardium.

In a further alternate unipolar embodiment of cardiac lead 20, innercable 28 is electrically conductive, and the proximal and distal cableends are electrically coupled by crimping or welding or other knowntechniques to connector pin 23 and helix fixation element 25,respectively. Inner sheath 29 electrically insulates inner cable 28 fromcoil 27, which acts only as a structural element to provide torsionalstiffness to lead body 21. Alternatively, the proximal and distal endsof the conductive inner cable 28 and the wire coil 27 can beelectrically connected together to provide a redundant unipolar leadconductors. Conductive inner cable 28 is preferably formed from wirestrands or filaments made of MP35-N alloy, well known in the art, or anyother bio-stable and biocompatible material that is capable of reliablyconducting electrical current after having been subjected to numerous,repeated bending and torsional stresses.

In a bipolar embodiment of cardiac lead 20, both coil 27 and inner cable28 are lead conductors as described above, that are electricallyinsulated from one another by inner sheath 29. In this embodiment, theproximal and distal ends of coil 27 are electrically and mechanicallycoupled by crimping or welding to the connector ring 32 and thering-shaped pace/sense electrode 30, respectively. The proximal anddistal ends of the inner cable 28 are electrically and mechanicallycoupled by crimping or welding to connector pin 23 and distal fixationhelix 25, respectively. The spacing 31 between ring-shaped pace/senseelectrode 30 and fixation helix 25 is between approximately 0.2 inchesand 0.4 inches, a range well known in the pacing art for inter-electrodebipolar pace/sense electrode spacing.

The exemplary active fixation cardiac lead 20 can also be formed havingan elongated cardioversion/defibrillation (C/D) electrode extendingproximally a predetermined distance along the outer sheath 21 from a C/Delectrode distal end located proximal to distal lead end 24. Theproximal and distal ends of the wire coil 27 would be electrically andmechanically coupled to the connector ring 32 and the elongated C/Delectrode, respectively. The proximal and distal ends of the inner cable28 would be electrically and mechanically coupled by crimping or weldingto connector pin 23 and distal fixation helix 25, respectively.

A means for steroid elution may be incorporated into any of theaforementioned embodiments of the exemplary active fixation cardiac lead20 near distal end 24. Such steroid elution means may take the form of amonolithic controlled release device (MCRD), constructed, for example,from silicone rubber and loaded with a derivative of dexamethasone, suchas the water-soluble steroid dexamethasone sodium phosphate. MCRDconstruction and methods of fabrication are found in commonly assignedU.S. Pat. Nos. 4,506,680, 4,577,642, 4,606,118, and 4,711,251.Alternatively a steroid coating containing a no more than sparinglywater-soluble steroid such as beclomethasone diproprionate ordexamethasone acetate may be applied to surfaces of ring-shapedpace/sense electrode 30 and/or fixation helix 25. A steroid coatingcomposition and method of application is found in commonly assigned U.S.Pat. No. 5,987,746. The steroid coating may be applied directly tosurfaces or portions of surfaces preserving structural integrity ofring-shaped pace/sense electrode 30 and/or fixation helix 25 and takingup less space than an MCRD.

Such an exemplary active fixation cardiac lead 20 can be employedadvantageously as a CS lead through the use of the bitumen guidecatheters of the present invention advanced through the pathway “A” ofFIG. 1 to locate the fixation helix 25 at a fixation site in thecoronary vasculature and to aim the helix tip 251 toward the heartbefore the connector assembly 22 is rotated to screw the fixation helix25 through the vessel wall and into the myocardium.

The guide catheters of the present invention enable the implantation ofa small diameter lead body 21 in the range of 1 French (0.33 mm) to 3French (1.00 mm), but it will be understood that the over-the-wire guidecatheters can be sized to facilitate implantation of larger diameterlead bodies exceeding 3 French in diameter. It will be understood thatthe guide catheters and methods of use disclosed herein can be employedto introduce and secure any form of distal fixation hooks or fixationhelices either extending distally like distal fixation helix 70 orlaterally from the lead body in the manner of those distal fixationhelices disclosed in U.S. Pat. Nos. 3,835,864 and 4,233,992, forexample. It will be understood that other active fixation cardiac leadshaving differing shaped fixation mechanisms, e.g., barbs or prongs orpins, can also be advantageously employed with the bilumen guidecatheters of the present invention. For example, the guide catheters ofthe present invention can be employed to locate the fixation mechanismat a fixation site in the coronary vasculature and to aim a fixationmechanism toward the heart before the proximal connector assembly or afurther device is activated or manipulated to advance and drive thefixation mechanism through the vessel wall and into the myocardium.

Turning to FIGS. 3-6, a first embodiment of an exemplary elongatedbitumen guide catheter 100 adapted to be used with a guide toolincluding a guidewire 80, for example, is illustrated. The guidewire 80extends between a guidewire proximal end 82 and a guidewire distal end84 and is adapted to be advanced through the tortuous pathway “A” fromoutside the patient's body to the implantation sites illustrated in FIG.1, for example. The bitumen guide catheter 100 depicted in FIG. 3includes an elongated catheter body 102 extending from a catheter bodyproximal end 112 joined with proximal handle or hub 110 to a catheterbody distal end 118. The elongated catheter body 102 has a length ofabout 25 cm to 120 cm depending upon the length of the selected pathwayfrom the skin incision through the patient's body to the implantationsite. The catheter body 102 further includes a proximal portion 108 anda distal portion or leader 120 that are joined together at junction 124as shown in FIG. 6. The distal leader 120 may have a length on the orderof about 10 mm to about 25 mm.

The bitumen guide catheter 100 receives a small diameter cardiac lead,e.g., cardiac lead 20, during the advancement of the catheter body 102through the tortuous pathway “A” and facilitates fixation of the distalhelix 25 at the selected implantation site as shown in FIG. 6. Theadvancement is facilitated by advancement of the small diameter distalleader 120 of the guide catheter 100 over the previously placedguidewire 80 past the selected implantation site.

The catheter body 102 therefore encloses a delivery lumen 114 extendingbetween a guide lumen entry port at the catheter body proximal end 112within the hub 110 and the catheter body distal end 118. The deliverylumen diameter is sized to receive the guidewire 80 inserted therein toaid in steering the guide catheter body 102 through the tortuous pathway“A”. The proximal portion of the catheter body 102 encloses deliverylumen 114 extending between a delivery lumen entry port at catheter bodyproximal end 112 within hub 110 and a delivery lumen exit port 134disposed along the catheter body proximal to the catheter body distalend 118.

To some degree, the disposition of the delivery lumen 114 and a guidelumen 116 extending side-by-side through a circular catheter body 108will cause the catheter body 102 to preferentially bend in a directionthat is transverse to a geometric axis plane AP (shown in FIG. 5)defined by the parallel lumen axes, particularly when advanced through atortuous pathway “A”. In one approach, the catheter body 102 is shapedto overcome that preferential bending tendency to cause the catheterbody 102 to preferentially bend in a fashion to bias the delivery lumenexit port 134 toward the vessel wall. Various shaping techniques andshapes are set forth in the preferred embodiments.

The proximal portion 108 is extruded into the shape depicted in FIG. 5,for example, to have a non-circular cross-section and to incorporateguide lumen 116 and delivery lumen 114. The non-circular cross sectioncan be achieved by a flange 104 presenting a flattened surface extendingalong at least a segment of the proximal portion 108 in a planeorthogonal or transverse to the axis plane AP defined by the axes of thedelivery and guide lumens 114 and 116. The flattened surface of flange104 has an extended width, for example, that encourages bending of theproximal portion 108 in one direction in the fashion of a belt. Theflattened surface of flange 104 can be formed alongside the guide lumen116 as shown in FIG. 5 or can be formed alongside the delivery lumen114. Or the catheter body can be shaped to have two generally parallelflat surfaces that are generally orthogonal to the plane defined by theaxes of the delivery and guide lumens 114 and 116. The flange 104 neednot extend the full length of the proximal portion 108 of the catheterbody 102 but may be present in a segment thereof that would be expectedto be advanced, in use, into a coronary blood vessel.

The catheter body 102 is reduced in cross-section area diameter in thedistal leader 120 extending between the delivery lumen exit port 134 andthe guide lumen exit port 136. The distal leader 120 can be tubular incross-section and tapered distally to facilitate advancement over theguidewire 80 extending through the guide lumen 116. Consequently, thesmall diameter leader 120 can be advanced readily over guidewire 80through twists and turns of the tortuous pathway and thereby guides theadvance of the larger cross-section proximal segment 108 of the catheterbody 102. The small diameter leader 120 can also be advanced deeply intonarrow pathways or passages to dispose the more proximal delivery lumenexit port 134 at a desired implantation site. The flattened surface 104encourages bending of the proximal portion 108 to track the contours ofthe heart and dispose the delivery lumen exit port 134 aimed toward theheart. The leader 120 can be straight or have one or more preformed bendalong the length thereof.

Then, as shown in FIG. 6, the fixation helix 25 can be advanced out ofthe delivery lumen exit port 134 extending away from the axis of thedelivery lumen 114 and toward the heart. The sharpened tip 251 of thefixation helix 25 can then be advanced, as the lead connector assemblyis rotated, through the vessel wall and into the underlying myocardium.Fixation is achieved as the fixation helix 25 is screwed into themyocardium.

FIG. 6 also illustrates a further form of shaping of a segment of thecatheter body 102 to bias the delivery lumen exit port 134 toward thevessel wall as the fixation helix 25 is advanced out of the deliverylumen exit port 134. The distal end of the delivery lumen is curved intoa guide bend 135 just proximal to the delivery lumen exit port 134 sothat the sharpened tip 251 extends toward the vessel wall as thefixation helix 25 is advanced out of the delivery lumen exit port 134.

The hub 110 (FIG. 3) coupled to the guide catheter proximal end 112 cantake the form of the hub disclosed in co-pending U.S. application Ser.No. 10/319,245. The hub 110 is advantageously formed with a hub deliverylumen mating to the delivery lumen proximal end opening and axiallyaligned with the catheter body delivery lumen 114. The hub deliverylumen extends through the hemostasis valve 140 and a hub guide lumendefined by a hub guide tube 122 extending through a side extension 132of the hub 110.

The hemostasis valve 140 includes a proximal rotating closure knob 142,an intermediate side port (extension hose and stopcock not shown) 144and a distal rotating locking collar (for securing valve to luer hubfitting) 146 that is press fit onto the hub 110. The knob 142 and sideport 144 and collar 146 are used in the fashion of a standard hemostasisvalve manufactured by numerous suppliers to shut off the flow and tolock the lead or other catheter in relation to the catheter body. Thevalve 140 provides a lead insertion lumen axially aligned with the hubdelivery lumen 148 so that a cardiac lead 20 of the types describedabove can be inserted therethrough and into the catheter body deliverylumen 114.

The hub guide tube 122 extends in an arcuate path through window 150 andthe side extension 132 that can also be coupled with a Luer typehemostasis valve to seal around the guidewire 80 in a manner well knownin the art. The hub 110 and the catheter body 102, particularly theproximal portion 108, are formed to be slittable along the lengthsthereof to exposed the aligned hub and catheter body delivery lumens andrelease the lead body of the cardiac lead 20 in a manner described inthe above-referenced '346 and '433 patents. An enlarged, relatively flatpad or paddle 130 is formed extending away from the hemostasis valve 140and the hub guide tube 122 that can be gripped on either side by thefingers to assist in holding and manipulating the hub 110 duringadjustment of the hemostasis valve 140 and advancement of the catheterbody assembly of the cardiac lead 20 and catheter body 102 through thetortuous pathway over the guidewire 80.

The guidewire 80 may have an outer diameter in the range of 0.014 to0.016 inches. The guidewire 80 can be a guidewire that is eitherintroduced by itself or is introduced through a separate, small diameterintroducer, e.g., a COOK® RoadRunner® Extra Support guidewire having anouter diameter of 0.018 inches (0.49 mm). The guidewire 80 can also be adeflectable or steerable guidewire of the type disclosed in commonlyassigned U.S. Pat. No. 4,815,478, for example.

The bilumen guide catheter 100 depicted in FIGS. 3-6 can also beadvanced through the tortuous pathway “A” of FIG. 1 employing astiffening stylet or steerable stylet substituted for guidewire 80inserted into guide lumen 116 to stiffen and selectively bend the distalleader 120 to during such advancement. In this variation, the guidelumen exit port is preferably closed or blocked by a block 138 toinhibit the ingress of blood and fluids.

A typical stylet includes a stainless steel wire extending between aproximal stylet wire handle and stylet wire distal end. The stylet wireis adapted to be advanced through the hub guide lumen 125 and thecatheter guide lumen 116 from outside the patient's body to abut thestylet distal end against the blockage 138 at the catheter body distalend 118. The stylet wire may have a stylet diameter of about 0.012 to0.016 inches. The stylet may be a steerable stylet, e.g., the MEDTRONIC®Model 9210 steerable stylet or a steerable stylet of the types disclosedin commonly assigned U.S. Pat. Nos. 5,873,842 and 6,146,338.

Certain embodiments of the bitumen catheter body 102 can advantageouslybe formed by extrusion of a single polymeric material without thenecessity of reinforcement or changing material characteristics alongits length. The bitumen catheter body 102 can be extruded from medicalgrade thermoplastic resins of 35D Shore durometer, for example, to formthe delivery tube 104 joined to a guide tube 106 at the elongatedjunction 108. A radiopaque marker band can be incorporated at thecatheter body distal end 118 at the distal tip of the distal leader 120.

The proximal portion 108 can be extruded from medical gradethermoplastic resins of 70D-75D Shore durometer, for example, and thedistal leader 120 can be extruded from medical grade thermoplasticresins of 75A-35D Shore durometer, for example. The durometer of theproximal portion 108 is therefore lower than the durometer of the distalleader 120. The higher durometer of the distal leader 120 enables it tobe formed having a thin sidewall so that the distal leader 120 can bemade smaller in diameter while providing a suitable guide lumen diameterto track a guidewire or receive a stylet or to be directed into smallerdiameter blood vessels or other body tracts. The harder surface of thehigher durometer material tends to have lower contact stress and, thus,presents lower friction to the guidewire. Moreover, the higher durometerdistal leader 120 can be shaped to have a pre-formed bend or curvaturethat is assumed upon retraction of the guidewire and assists in urgingthe delivery lumen exit port 134 toward the heart. The medical gradethermoplastics can be selected from polyether block amide (PEBA),polyamide (PA), polyurethane (PU), polyester (PET), polybutyleneterephthalate (PBT), or polyvinyl chloride (PVC). Optimally, theproximal portion 120 can be extruded from one of the group consisting ofPEBA, PU, PET or PVC having a relatively low durometer, whereas thesmaller diameter distal leader 120 can be extruded from the groupconsisting of PEBA, PU, PA, PET, PBT or PVC having a relatively higherdurometer.

In addition to the radiopaque marker band, an atraumatic soft tip can beapplied at the catheter body distal end 118. The soft tip can be formedof a polyurethane, e.g., TECOFLEX® TT-1074A polyurethane sold byThermedics Polymer Products, Inc., Woburn, Mass. The polyurethanematerial can be loaded with a radiopaque material, e.g. barium sulfateor tungsten powder, to make the resulting molded soft tip radiopaque.

The surfaces of delivery lumen 114 and guide lumen 116 may be coatedwith a lubricant to facilitate advancement of a cardiac lead 20 or otherinstrument through the delivery lumen 114 and the guidewire 80 or styletwire or other instrument through the guide lumen 116. The exteriorsurface of a distal portion of the catheter body 102 including thedistal leader 120 can also be coated with the lubricant to facilitateadvancement of the distal leader 120 through the tortuous pathway.Suitable biocompatible lubricating coatings include a silicone-basedlubricant, e.g., a silicone oil, or a reactive silicone lubricant, e.g.,MDX4-4159 silicone lubricant available from Dow Chemical Co., Midland,Mich. Other suitable biocompatible lubricating coatings includehydrophilic slip coating materials, e.g., polyacrylamide,polyvinylpyrrolidone, hyaluronic acid, or polyethylene oxide.

Referring to FIGS. 7 and 8, a further embodiment of the guide catheter100, particularly having a further catheter body 202 including aproximal portion 208 and a distal leader 220, is shown. In thisembodiment, the proximal portion 208 of catheter body 202 is extrudedinto a substantially oval or rectangular cross-section shape havingopposed major, substantially flat, sides 204 and 205. The delivery lumen214 and guide lumen 216 extend side-by-side through the proximal portion208 between the major sides 204 and 205. The parallel axes of thedelivery lumen 214 and guide lumen 216 define a geometric axis plane AP,and the major sides 204 and 205 extend substantially in parallel withthe axis plane AP. A short distal segment of the delivery lumen 214 isshifted out of side-by-side alignment with a corresponding segment ofthe guide lumen 216 to dispose the delivery lumen exit port 234 above oralongside the major side 204. The axis plane AP is in effect twistedfrom a first orientation prevailing in the proximal segment of theproximal portion 208 into a second orientation near the delivery lumenexit port 234 (as shown in FIGS. 7 and 8) that is substantiallytransverse to the first orientation. The distal end of the deliverylumen 214 can be shaped with a curved guide bend 135 of the typedepicted in FIG. 6.

As shown in FIG. 8, the opposed major sides 204 and 205 tend to causethe catheter body 202 to advance through the coronary vasculature overthe guide tool, e.g., the guidewire 80, within the guide lumen 216 withthe delivery lumen exit port 234 disposed toward the heart. A curve 221is preferably pre-formed in the distal leader 220 extending away fromthe major side 205 that tends to offset the shift of the delivery lumenexit port 234 into alignment with the major side 204 and to dispose thedelivery lumen exit port 234 toward the heart, particularly themyocardium of the LV 7 as also shown in FIG. 8.

The delivery lumen 214 and the guide lumen 216 can constituteco-extruded tubes of the materials described above. The connectionbetween the co-extruded tubes can be severed along the length of thedistal segment of the delivery lumen 214. The distal ends of theco-extruded tubes can be cut to length to form the distal leader 220 andto dispose a short segment of the tube surrounding the delivery lumen214 over a proximal segment of the tube surrounding the guide lumen 216.Or, a distal segment of the proximal portion 208 and the distal leader220 can be molded as a separate assembly that is adhered to a distal endof the substantially rectangular cross-section extrusion to form thecatheter body 202.

A jacket 240 of flat metal or plastic filaments may be braided over theouter surface of the proximal portion 208 of the catheter body 202 thatfurther assists in causing the catheter body to preferentially bend tobias the delivery lumen exit port 234 toward the heart. A thin coatingof elastomeric material can be fitted over the jacket 240 to make itsexterior surface smooth.

Referring to FIGS. 9 and 10, a still further embodiment of the guidecatheter 100, particularly a further catheter body 302 having at leastone further lumen, is shown. In particular, an additional delivery lumen317 is provided in the catheter body proximal portion 308 thatterminates in a further delivery lumen exit port 335. The proximalportion 308 of catheter body 302 is relatively cylindrical toaccommodate three lumens 314, 316 and 317. However, shaping of thecatheter body 302 to urge the delivery lumen exit ports 334 and 335toward the heart is accomplished by shapes formed in segments of theproximal and distal portions 308 and 320 that collectively have ashallow “S” shape including pre-formed bends 319, 321 and 323 as shownin FIG. 10.

Referring to FIGS. 11-14, a still further embodiment of the guidecatheter 100, particularly a further catheter body 402 having aninternal shaping structure, is depicted. In this embodiment, theproximal portion 408 of catheter body 402 is formed of a generallycylindrical outer sheath 442 that encloses a generally oval orrectangular or triangular cross-section, bitumen tube 438 having opposedmajor sides 404 and 405. A delivery lumen 414 and guide lumen 416 extendside-by-side through the tube 438 in proximal portion 408 between themajor sides 404 and 405. Two examples of the cross section of bilumentube 438 are shown in FIGS. 12 and 14 where the major sides 404 and 405are spaced from and extend substantially parallel to the axis plane AP.

A jacket 440 of flat metal or plastic filaments may be braided over theouter surface of the tube 438 in proximal portion 208 of the catheterbody 202 that further assists in causing the catheter body 202 topreferentially bend to bias the delivery lumen exit port 234 toward theheart. In this embodiment, the generally cylindrical outer sheath 442 isformed over the jacket 440 to make the proximal portion 408 of catheterbody 402 generally cylindrical.

A short distal segment of the delivery lumen 414 is shifted out ofside-by-side alignment with a corresponding segment of the guide lumen416 to dispose the delivery lumen exit port 434 above or alongside theflat side 404 in the manner described above with respect to theembodiment of FIGS. 7 and 8. The distal end of the delivery lumen 414can be shaped with a curve like guide bend 135 depicted in FIG. 6.

In this way, the shape of the jacket 440 tends to cause the catheterbody 402 to advance through the coronary vasculature over the guidetool, e.g., the guidewire 80, within the guide lumen 416 with thedelivery lumen exit port 434 disposed or biased toward the heart. Acurve 421 is preferably pre-formed in the distal segment 420 extendingaway from the flat side 405 that tends to offset the shift of thedelivery lumen exit port 434 into alignment with the flat side 404 andto dispose the delivery lumen exit port 434 toward the heart,particularly the myocardium of the LV 7 as also shown in FIG. 12.

FIG. 15 is a cross-sectional view of a catheter body according to anembodiment of the present invention. As illustrated in FIGS. 3 and 15, acatheter body 502 of a guide catheter 500 according to an alternateembodiment of the present invention includes and extends from thehemostasis valve 140 and hub 110 as described above. Similar to thecatheter body described above, the catheter body 502 includes a proximalportion 508 extending from the hemostasis valve 140 and hub 110 to adistal end 509, and a distal portion or leader 520 extending from aproximal end 511 to a catheter body distal end 518, with the distal end509 of the proximal portion 508 and the proximal end 511 of the leader520 being joined together at a junction 524.

According to an embodiment of the present invention, the leader 520 hasa length extending from the proximal end 511 to the distal end 518 andthe proximal portion 508 has a length extending from the hemostasisvalve 140 and hub 110 to the distal end 509 that is dependent upon theselected pathway through the patient to the implantation site.

The proximal portion 508 of the guide catheter 500 includes an outerwall 504 that forms a lumen 506 that extends within the proximal portion508 of the catheter body 502 from the proximal end 112 of the catheterbody 502 to the distal end 509 of proximal portion 508, forming anopening 522 at the distal end 509. Similarly, the leader 520 includes anouter wall 522 that forms a lumen 528 in the catheter body 502 thatextends from the proximal end 511 of the leader 520 to the distal end518, and forms an opening 530 at the distal end 518 of the catheter body502. The outer wall 504 of the proximal portion 508 includes a taperedportion 530 that extends from a tapered portion proximal end 532 to thedistal end 509 of the proximal portion 508 of the catheter body 502 sothat the opening 522 at the distal end 509 of the proximal portion 508is axially aligned at the junction 524 with and in fluid communicationwith the lumen 528 and the opening 522 has a diameter approximatelyequal to the diameter of the lumen 528 extending within the leader 520.

An inner wall 540 is positioned within the lumen 506 of the proximalportion 508 of the catheter body 502 spaced from an inner surface of theouter wall 504 to form an inner lumen 542 that extends from the proximalend 112 of the catheter body 502 to a distal end 544 of the inner wall540 and forms an opening 546 at or proximal to the tapered portion 530of the outer wall 504. Similarly, the inner wall 540 is spaced from anopposing inner surface of the outer wall 504 to form a second innerlumen 548 that extends from the proximal end 112 of the catheter body502 to the distal end 544 of the inner wall 540 and forms a secondopening 550 at or proximal to the tapered portion 530 of the outer wall504.

According to an embodiment of the present invention, a stylet or guidewire 552 is advanced though inner lumen 542 to extend outward fromopening 546 along the inner surface of the outer wall 504 at the taperedportion 530 and outward from the distal end 518 of the catheter 500during navigation of the catheter 500 to a desired site in the patient.Once the catheter 500 has been positioned at the desire site, theguidewire 552 is retracted by being advanced inward within the catheterbody until a distal tip is proximal to the tapered portion 530 withinthe lumen 506. A lead 554 is then advanced through the second innerlumen 548 to extend outward from the second opening 550 along the innersurface of the outer wall 504 at the tapered portion 530 and outwardfrom the distal end 518 of the catheter 500 to the desired site in thepatient. The catheter 500 and guidewire 552 are then removed from thepatient, leaving the lead in place at the desired site.

FIG. 16 is a cross-sectional view of a catheter body according to anembodiment of the present invention. As illustrated in FIG. 16,according to an embodiment of the present invention, a lumen 642 isformed using a separate tube member 600 that is fixedly engaged againstthe inner surface of the outer wall 504 and extending from the proximalend 112 of the catheter body 502 to a distal end 644 of the tube member600 and forms an opening 646 at or proximal to the tapered portion 530of the outer wall 504. The tube member 600 is spaced from the opposinginner surface of the outer wall 504 to form a second inner lumen 648that extends from the proximal end 112 of the catheter body 602 to thedistal end 644 of the tube member 600 and forms a second opening 550 ator proximal to the tapered portion 530 of the outer wall 504.

According to the present invention, a tube member could be utilized toform the second lumen 648 that is utilized for receiving the cardiaclead, rather than the inner lumen 642 that is utilized for receiving theguide tool shown in FIG. 16. In addition, markers could be includedalong the outer surface of the catheter that could be utilized to assistin determining the position of the lead or the guidewire, usingfluoroscopy, as the lead and guidewire are advanced and retracted withinthe catheter.

The two lumens of the present invention provide the ability to moreeasily switch between advancing the guide tool outward from the distalend of the catheter and advancing the lead outward from the distal endof the lead, reducing the likelihood that the catheter position will becorrupted when the guide tool is retracted or the lead is advanced. Inaddition, the tapered portion of the catheter serves to improve accessto cardiac veins. It is understood that while the present invention isdescribed above in terms of placing the lead within the coronary veins,the present invention is not intended to be limited to left heart leadplacement but rather may also be utilized for placing leads to otherlocations in the patient, including, for example, the right ventricle orthe right atrium of the heart.

These embodiments of bilumen and multi-lumen guide catheters 100 can beemployed in a variety of procedures for introducing cardiac leads intocoronary veins of the heart, e.g., deep in the cardiac veins descendingfrom the coronary sinus accessed transvenously and through the coronarysinus as illustrated in FIG. 2, to lodge the distal pace/sense electrodein relation to the left ventricle. The guide catheters 100 can also beemployed to fix a pace/sense electrode at certain particular sites in aheart chamber, e.g., the right ventricular outflow tract.

Further instruments or diagnostic fluids can be selectively advancedthrough the delivery lumen and/or the guide lumen to facilitateidentification or advancement of the catheter body distal end to theimplantation site preceding the advancement of the cardiac lead throughthe delivery lumen.

The guide catheter having an open guide lumen exit port canadvantageously be used to perform other functions, e.g., to facilitateblocking of a cardiac vessel employing a balloon catheter so thatradiopaque diagnostic fluid can be introduced into the cardiac vessel tovisualize the cardiac vessel in an angiographic procedure in order toidentify a suitable implantation site.

All patents and publications identified herein are incorporated hereinby reference in their entireties.

While particular embodiments of the invention have been disclosed hereinin detail, this has been done for the purposes of illustration only, andis not intended to limit the scope of the invention as defined in theclaims that follow. It is to be understood that various substitutions,alterations, or modifications can be made to the disclosed embodimentswithout departing from the spirit and scope of the claims. The abovedescribed implementations are simply those presently preferred orcontemplated by the inventor, and are not to be taken as limiting thepresent invention to the disclosed embodiments. It is therefore to beunderstood, that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described withoutactually departing from the spirit and scope of the present invention.

1. A guide catheter for introducing a cardiac lead having a distalfixation mechanism through a pathway from an incision to an implantationsite, comprising: an elongated catheter body extending between a firstproximal end and a first distal end, the catheter body including anouter wall and a distal leader and having a proximal portion extendingfrom the first proximal end to a second distal end, the distal leaderextending distally from the second distal end, and the outer wallextending along the proximal portion and the distal leader and formingan outer lumen extending through the proximal portion and the distalleader; and an inner member positioned within the outer lumen and havinga third distal end, the inner wall spaced from the outer wall to form afirst inner lumen for receiving a guide tool inserted therein to aid insteering the catheter body through the pathway and a second lumen forreceiving the cardiac lead while the guide tool is positioned within thefirst inner lumen, the third distal end forming a first opening at adistal end of the first inner lumen and a second opening at a distal endof the second inner lumen, the first opening and the second openingpositioned proximal the distal leader.
 2. The guide catheter of claim 1,wherein the outer wall includes a tapered portion for directingadvancing of a distal tip of the guide tool from a retracted positionproximal the third distal end to an extended position within the outerlumen of the distal leader while a distal tip of the lead is positionedin the retracted position, and for directing advancing of the distal tipof the lead from the retracted position to the extended position whilethe distal tip of the guide tool is positioned in the retractedposition.
 3. The guide catheter of claim 1, wherein the distal fixationmechanism includes one of a fixation helix adapted to be screwed througha vessel wall into the myocardium, a hook, and a prong adapted to beextended through the vessel wall into the myocardium.
 4. The guidecatheter of claim 1, further comprising a tubular member extendingwithin the outer lumen along the proximal portion, wherein the innermember is formed by the tubular member.
 5. The guide catheter of claim1, wherein the outer wall includes a tapered portion extending from atapered portion proximal end to the second distal end so that a lumenopening formed at the second distal end is axially aligned with and hasa diameter approximately equal to a diameter of the outer lumen formedby the outer wall along the distal leader, and wherein the third distalend is proximal the tapered portion.
 6. The guide catheter of claim 1,wherein the guide tool is one of a guidewire, a stiffening stylet, and asteerable stylet.
 7. The guide catheter of claim 1, wherein the distalfixation mechanism includes one of a fixation helix adapted to bescrewed through a vessel wall into the myocardium, a hook, and a prongadapted to be extended through the vessel wall into the myocardium.
 8. Amethod of introducing a cardiac lead having a distal fixation mechanismthrough a pathway from an incision to an implantation site, comprising:positioning one of a guide tool and the lead in a first inner lumen of aguide catheter formed by an inner member positioned within a portion ofan outer lumen extending through a proximal portion of the guidecatheter, the inner member formed by an outer wall of the guide catheterand spaced from the outer wall; positioning the other of the guide tooland the lead in a second inner lumen of the guide catheter formed by theinner member and the outer wall; advancing the guide catheter throughthe pathway; advancing a distal tip of the guide tool from a retractedposition proximal to a distal end of the inner member to an extendedposition within and extending outward from a portion of the outer lumenformed by the outer wall along a distal leader extending distally fromthe proximal portion of the guide catheter and to the implantation site;advancing the guide catheter over the guide tool to the implantationsite; advancing the guide tool from the extended position to theretracted position; and advancing the fixation mechanism of the leadfrom the retracted position to the extended position.
 9. The method ofclaim 8, further comprising fixedly engaging the fixation mechanism atthe implantation site.
 10. The method of claim 8, wherein the outer wallincludes a tapered portion extending from a tapered portion proximal endto a distal end of the proximal portion of the guide catheter so that alumen opening formed at the distal end of the proximal portion isaxially aligned with and has a diameter approximately equal to adiameter of the outer lumen formed by the outer wall along the distalleader, and wherein the distal end of the inner member is proximal thetapered portion and the tapered portion directs the advancing of theguide tool and the lead between the retracted position and the extendedposition.
 11. The method of claim 8, wherein the guide tool is one of aguidewire, a stiffening stylet, and a steerable stylet.
 12. The methodof claim 8, wherein the inner wall is formed by a tubular memberextending within the outer lumen along the proximal portion of the guidecatheter.
 13. The method of claim 8, wherein the distal fixationmechanism includes one of a fixation helix adapted to be screwed througha vessel wall into the myocardium, a hook, and a prong adapted to beextended through the vessel wall into the myocardium.
 14. The method ofclaim 8, wherein the inner member is formed by a tubular member
 15. Aguide catheter for introducing a cardiac lead having a distal fixationmechanism through a pathway from an incision to an implantation site,comprising: an elongated catheter body extending between a firstproximal end and a first distal end, the catheter body including anouter wall and a distal leader and having a proximal portion extendingfrom the first proximal end to a second distal end, the distal leaderextending distally from the second distal end, and the outer wallextending along the proximal portion and the distal leader and formingan outer lumen extending through the proximal portion and the distalleader; and an inner member positioned within the outer lumen and havinga third distal end, the inner wall spaced from the outer wall to form afirst inner lumen for receiving a guide tool inserted therein to aid insteering the catheter body through the pathway and a second lumen forreceiving the cardiac lead while the guide tool is positioned within thefirst inner lumen, the third distal end forming a first opening at adistal end of the first inner lumen and a second opening at a distal endof the second inner lumen, the first opening and the second openingpositioned proximal the distal leader, wherein the outer wall includes atapered portion extending from a tapered portion proximal end to thesecond distal end so that a lumen opening formed at the second distalend is axially aligned with and has a diameter approximately equal to adiameter of the outer lumen formed by the outer wall along the distalleader, and wherein the third distal end is proximal the taperedportion, the tapered portion directing advancing of a distal tip of theguide tool from a retracted position proximal the third distal end to anextended position within the outer lumen of the distal leader while adistal tip of the lead is positioned in the retracted position, anddirecting advancing of the distal tip of the lead from the retractedposition to the extended position while the distal tip of the guide toolis positioned in the retracted position.
 16. The guide catheter of claim15, wherein the distal fixation mechanism includes one of a fixationhelix adapted to be screwed through a vessel wall into the myocardium, ahook, and a prong adapted to be extended through the vessel wall intothe myocardium.
 17. The guide catheter of claim 15, further comprising atubular member extending within the outer lumen along the proximalportion, wherein the inner wall is formed by the tubular member.
 18. Theguide catheter of claim 15, wherein the guide tool is one of aguidewire, a stiffening stylet, and a steerable stylet.